In normal use, a skid-steer loader has a loader bucket pivotally attached to two front lift arms. Optionally, the loader bucket of a skid-steer loader may be removed and alternate or auxiliary implements such as a planer may be attached to grind and remove hard surfaces such as pavement surfaces of concrete or asphalt such as in roads, bridges or parking lots. Such planers are sometimes called cold planers.
Common apparatus for grinding or planing away hard level surfaces such as asphalt roads or concrete roads commonly drive a rotating grinding cylinder or drum, the exterior surface of the drum has a multiplicity of cutters for grinding and cutting, typically teeth or carbide or diamond tipped cutters. The cutters can be replaced as they wear out. Such a grinding drum is commonly driven and controlled by a hydraulic machine which provides supporting and driving mechanisms for pressing the grinding drum against a flat surface to be ground or planed away, for rotatably driving the grinding drum causing its cutters to impinge upon the surface to be ground away, and for moving the grinding drum in a forward motion along the surface being ground. Typically, a cold planing apparatus incorporates a protective shroud to shield against flying debris.
In many cases, a surface planer is used to remove an area of material at a constant depth. In one version of the prior art, illustrated in FIG. 2A, a grinder arrangement 50 is configured with a series of circular plates 52 vertically arranged and perpendicular relative to a shaft or axle. A series of cutters 54 such as grinding teeth are supported by and arranged around the perimeter of the plates. The plates 52 have a constant diameter. The cutting width of each plate is limited by the orientation of cutters 54. For example, each plate may only be able to cut a width of 1½ to 2 inches. When used, as illustrated in FIG. 2B, grinder arrangement 50 forms a cutting pattern formed as a single continuous slot 55 at an even depth. To form a continuous slot 55, the paths of respective cutters 54 of adjacent plates 52 must be closely spaced and/or overlap to avoid leaving a grooved surface. However, the plate spacing is limited due to the physical mounting arrangement. The maximum width is also limited because power and mounting requirements limit the number of plates 52 which can be used. Further, a drawback or disadvantage of such grinding drums is that pulverized asphalt or concrete debris tends to pile up in front of and behind the grinding drum as it moves forward, creating unwanted resistance to forward motion and drum rotation, wasting energy and causing excess wear by re-grinding of the debris.
An improvement on grinder 50 with vertical plates is the elliptical disc arrangement disclosed in U.S. Pat. No. 5,791,737. An example is illustrated in FIG. 3A. The elliptical disc grinder arrangement 60 includes an axle having four elliptical grinding discs 62 mounted thereon. A multiplicity of hardened grinding teeth or cutters 64 are spaced at intervals along the outer peripheral surfaces of the elliptical discs.
The elliptical plates 62 are tilted and fixed with respect to the axle. An elliptical plate 62 can be angled so that the path of its perimeter defines a cylindrical section relative to a shaft. When viewed along the axis of the shaft, the ellipse appears to be a circle. When such an elliptical plate is rotated about the shaft axis, all points on the ellipse edges orbit equidistant from the axis and the rotation defines a cylindrical section with a height and radius. The cutter paths all have the same radius around the axis of rotation, but may be offset laterally along the axis thus determining the cylindrical section height. The paths may be closely spaced or may overlap while the cutters are spaced in different spots along a shared orbit. This creates a continuous slot 65 of even depth (FIG. 3B). The tilted elliptical plates 62 allow a wider path to cut by each plate and its associated cutters. For example, each plate may cut a pattern in a width of 4 to 6 inches. The plate and cutter spacing also allows pulverized debris to pass between the plates to exit the grinder.